The invention is directed to a method and to a system for routing in the connection setup for calls between a first subscriber and a second subscriber who moves between coverage areas of mobile switching centers of a public mobile radio telephone network and areas of private branch exchange devices of one or more private networks.
A public mobile radio telephone network such as, for example, the international mobile radio telephone network according to the GSM standard (Global System For Mobile Communication) offers, as known, mobile subscriber telephone services, data services and additional services that, for example, are also known from the ISDN network (Integrated Services Digital Network) and can be connected to further networks, for example the public telephone network (PSTN) or the ISDN network or some other line-bound network. Connections from and to other public mobile radio networks are also supported. The GSM mobile radio telephone network is a digital radio communications system cellularly constructed of a great number of radio cells. Each radio cell is thereby serviced by a base transmission-reception station that respectively sets up the connections to the mobile stations of the subscribers via the air interface. One or more base transmission-reception stations are managed by a base station controller.
One or more base station controllers are respectively connected to a mobile switching center that assumes the switching-oriented functions for a specific coverage area in the mobile radio telephone network. The switching-oriented functions include routing, i.e. the selection of routes, and the setup of connections for signaling and for call-through connection. Over and above this, the mobile switching center implements specific mobile radio telephone functions that derive from the mobility of the subscribers. Included here is the mobility administration of the mobile subscribers in the respective coverage area. The mobile switching center has a subscriber data base allocated to it in which subscriber data and location information for the subscribers that are in the coverage area are stored. The subscriber data base, for example, assumes functions of call handling, of connection setup and, in particular, of location registration. A location area identity according to the GSM standard is usually entered into the subscriber data base for the mobile subscriber.
The article "Einen Schritt Naher am Personal Communicator", telcom report 18, 1995, pages 308-309 discloses that wire-bound subscribers, for example ISDN subscribers, who are connectible via private branch exchanges be serviced by the mobile switching center--in addition to mobile radio telephone subscribers--in a combined operating mode. Connections thus arise between mobile switching centers of the public mobile radio telephone network and private branch exchange equipment of one or more private networks. For example, a number of locations of a company or of a number of companies are connected to one another in the private network (corporate network). The networks are not treated equally at the present time in the cooperation of the private network with the public mobile radio telephone network, i.e. the one network is respectively used only as access network for the other network. What this means in view of the routing given calls that relate to subscribers who can move between mobile radio telephone network and private network or within the respective network is that the routing for a call must be conducted via the public mobile radio telephone network in the call setup when originating private branch exchange equipment--to which the call is routed because of the selected telephone number--and destination private branch exchange equipment--at which the called subscriber can be reached or a substitute destination is deposited for him--lie in the same private network. Since the private branch exchange equipment are usually networked with one another, the connection to be set up via the public mobile radio telephone network does not represent an optimum method for routing.
It is therefore an object of the present invention to specify a method and a system for optimized routing between private branch exchange equipment of a private network supported by the public mobile radio telephone network. With respect to the method, this object is inventively achieved by the features of patent claim 1, and is achieved with respect to the system by the features of patent claim 13. Developments of the invention are recited in the subclaims.
In accord therewith, at least one identification number for the identification of a private network for access to a first private branch exchange equipment from which a call to a subscriber was registered and a mobile subscriber telephone number was transmitted into the public radio telephone network is stored in the public mobile radio telephone network. A routing number is offered in the mobile radio telephone network on the basis of the incoming mobile radio telephone subscriber telephone number and is checked with respect to the stored identification number to see whether the call destination lies in the area of a private branch exchange equipment of the same private network to which the first private branch exchange equipment belongs. When this is the case, routing information that define the call destination are sent--after cleardown of the call in the public mobile radio telephone network--to the first private branch exchange equipment that subsequently sets up the connection to the call destination on the basis of the received routing information in the private network.
As a result of the method and the system according to the invention, the public mobile radio telephone network supports an optimum routing in the connection setup within the private network when the originating private branch exchange equipment (home private branch exchange equipment) at which the call is registered for the call subscriber and the destination private branch equipment (visitor private branch exchange equipment) in which the call destination lies when, for example, the called subscriber is booked there or a substantive destination is registered for him, lie in the same private network. A complicated routing via the public mobile radio telephone network is avoided in the connection setup between originating private branch exchange equipment and destination private branch exchange equipment. The advantage of the inventive method or, respectively, system is also comprised therein that the call forwarded to the public mobile radio telephone network because of a mobile radio telephone subscriber telephone number is in turn cleardown via the network-overlapping interface between private network and mobile radio telephone network before the routing is setup between the private network from the originating private branch exchange equipment to the destination private branch exchange equipment on the basis of the routing information that have been communicated. The result is a lower time requirement in the connection setup on the basis of an optimized routing as well as a lower load on the network equipment effected by the routing in the public mobile radio telephone network.
According to a development of the invention, a routing number is offered in the public mobile radio telephone network, this at least comprising an identification number for identifying the private network in which the private branch exchange equipment of the call destination lies. It is advantageous when the routing number additionally contains an identification number for identifying the private branch exchange equipment of the call destination and an identification number for identifying the connection port of the private branch exchange equipment.
It is also advantageous when the routing information employed for the connection setup between the private branch exchange equipment of the same private network comprise an identification number for identifying the private branch exchange equipment of the call destination and an identification number for identifying the connection port of the private branch exchange equipment.
According to another development of the invention, a location information that indicates how the subscriber can be reached in the area of a private branch exchange equipment of the private network is stored and is employed as routing number for a comparison to the stored identification number with respect to identity of the private network for the first private branch exchange equipment and for the private branch exchange equipment that registers the called subscriber.
According to an alternative development of the invention, the routing number, due to a call redirection, is employed for comparison to the stored identification number in view of the identity of the private network for the first private branch exchange equipment and for the private branch exchange equipment of the call destination.
According to alternative developments of the invention, the comparison of the routing number to the identification number is implemented by a service control unit of an intelligent network that is linked into the public mobile radio telephone network by connection to at least one mobile switching center or is implemented by a mobile switching center that registers the access to the first private branch exchange equipment. When the comparison yields an identity of the private network for the private branch exchange equipment, the routing information are transmitted from the mobile switching center to the private branch exchange equipment via the network-overlapping interface.